Turbine blading



WITNESSES: I NVENTOR F. HODGKINSON TURBINE. BLADING -Filed s 'i. 12. 1923 s sfieets-sheet 1 I". Hadzlu'na oh ATTORNEY Aug. 24-, 1926. 4

F. HODGKINSON TURBINE BLADING' Filed Sept. '12. 1923- 3 Sheets-Sheet 2 4 ATTORNEY Patented Aug, 24, 1926. l

UNITED STATES! FRANCIS noneKIN'so v, or swanrnlvionn, rnnnsy vania, AssIGNoR T wns'ri qe- HQUSE ELEQTBIC AND MANUFACTURIIIQ QQMlAlnQ ,A QOBI'QRATWN 0F PEZNIY'Y s AN e,

'IURBZNE BLADING.

Application filed September 12, 1923. Serial No. 562 324,

My invention relates to elastic-fluid turbines, more particularly to low-pressure blading therefor, and it has for its object to provide apparatus of the character designated wherein terminal losses may be re duced or the capacity of the turbines for the production of power increased.

' The height of turbine blades for a given drum diameter is limited from the standpoint of efliciency, on account of the clifference in speeds between the tip and root portions thereof which cannot be efficiently satisfied by a single steam velocity. In accordance with my invention, I provide additional or shorter blading following tall low-pressure blading' and which serves to abstract the available portion of the residual energy possessed by steam discharged from the inner portions of the tall low-pressure blading.

Preferably, when the differences between tip and root speeds of the blading exceeds a desired amount, partition members are provided which divide the blades into inner and outer tiers and which segregate the steam passing t-herethrough int-o inner and outer portions or annuli, This arrange: ment provides two turbine paths, the blading of which'operates different velocities.

Owing to the higher blade velocity of the outer tier, the steam in the outer path or annulus may have suflicient turbine elements moving at a su table velocity wlth respect to the steam velocity to abstract the maxi mum amount of the available energy from the outer annulus or path of steam, whereas, the inner tier, due to its lower blade velocity, cannot abstract the same amount of energy as the outer tier in the same number of rows. Additional blading is, therefore, provided. to abstract the available portion of the residual velocity energy from the inner portion of steam discharged from the inner portions of the blades of the last tall moving row.

lVhile low-pressure turbinesections con sisting of tiered blading to, provide separate which is made in tiers in order to avoid terminal losses due to differences in speed between the moving blade tip and root portions. In the Baumann patent referred to, the object is to provide greater leaving area for the terminal moving blades so that terminal blading having smaller and more eiiicient exit or discharge angles be employed. Hence, in the Baumann construe tion, the inner tiers, until the terminal stages are reached, serve, in effect, merely as com duits for supplying steam to the latter. On the other hand, in my construction, since my object is to reduce terminal losses, incident to velocity differences of root and tip por tions of blading, which is relatively tall for a given drum diameter, the inner tier is effective in absorbing energy from the steam; and, preferably, the effectivenessof my in ner tier is limited only by the necessarily slower moving blade elements thereof as compared to the outer tier.

Apparatus embodying features of my in vention is illustrated on the drawings, forming a part of this application, in which Fig. 1 is a sectional view of a turbine showing my improved form of b-lading applied there to; Figs. 2 and 3 are views similar to Fig, 1, but showing slightly different modified forms of b-lading;*Fig. shows a further modified form of my invention in which the partition members for the tall blading are omitted; Fig. 5 is a sectional line taken along the line VV,of Fig. 1; Fig. 6 is a detail view showing packing suitable for use in certain of the constructions referred to and Fig. 7 is a view along a row of tiered blades illustrating the partition wall ele ments defining the tiers.

Referring now to the drawings for a better understanding of my invention, I show in Figs. 1, 2-, and 3 av turbine consisting of a casing 10 and a rotor 11 having blading of any suitable type followed by a tiered section, at 12, having inner and outer tiers of blade elements, at 13 and 14, respectively. The 'inner tier of blade elements, at 13, is followed by additional blading, at 15, for abstracting the available portion of the residual energy from steam discharged from the inner tier.

Referring now more particularly to Fig. 1, I show the tiered sectiomat 12, comprised by rows of stationary blades 16, 17, 18 and 19 carried by the casing 10 and followed respectively, by the moving rows of blades 20, 21, 22 and 23. The blades 16, 17, 18, 19, 20, 21, 22 and 23 are, respectively, provided with partition or wall elements 25, 26, 27, 28, 29, 30 and 31 which cooperate to define said inner and outer tiers, at 13,

37 which also serves as a deflector for the annulus of steam discharged by the outer tler blachng and as a shroud or cover for the tips of the blades 36. The shroud element 3'? is preferably supported from the casing 10 by means of webs 38 wh1ch do not interfere with thefree discharge of steam fro-m the outer tier, at 14.

The outer portions 40 and 41 ofthe stationary and moving blades 19 and 23, respectively, may be of the impulse type, the

I last drop in pressure for the outer tier, at

14, taking place through the outer blade portions 40. The inner portions 42 and 33 of the rows of blades 19 and-23 may each have drops in pressure or expansion of steam thereacross, in which case the pressure at the discharge side of the blade portions 42 would be greater than 'DllGxPlGSSHIG at the discharge side of the, blade portions 40 of the same, row-of stationary blades 19, there by necessitating the use of packing 44 between the partition or wall elements 30 and 31 to prevent leakage from the inner tier, at 13, to the outer tier, at 14. V

The inner blade portions 33 of the row of blades 23 may expand steam to exhaust pressure, namely,the discharge pressure of the outer portions 41 of the same row of blades.

23, in which case the blades35 serve merely as redirecting vanes to properly impinge steam against impulse blades 36; however, asillustrated in Fig. 1, a drop in pressure or expansion of steam is contemplated across the row of blades or vanes 35, in which case, the discharge pressure of the inner blade portions 33 is higher than the pressure of the outer portions 41 of the same row of blades 23, thereby necessitating the employment of packing 45 between the partition or wall elements 31 and the detector or shroud element 37v to prevent steamdischarged by the inner blade portions 33 fromleaking.

directly to the exhaust. r H

The blades or vanes 35 increase in height from. the inlet to the exit sides .in order'to provide for adequate flow areaand the dis charge of steam at a small angle, the latter feature resulting in narrowing of steam passages as will be clear from Fig.- 5, from which it will be seen that the normal passage width decreases from the inlet to the exit sides of the blades or vanes 35. The blade portions 41 and the blades 36 increase in height from the inlet to the exit sides thereof sufficiently to provide adequate area for the passage of steam owing to the decreasing velocity of the latter as it passes therethrough.

In Fig. 2, I show a modified form of my invention in which all of the bla-ding is of the reaction type. In other words, the blade portions 35, 36 and 41 are. of the reaction type, that is, a drop in pressure of steam takes placeacross each of these rows. Since the inner tier, at 13, and the additional blading, at-15, constitute a greater number of energy-abstracting stages than are in the outer tier, at 14, the pressure distributions must be dilferent,'that is, the pressures at the discharge sides of the blades 16, 17, 18

and 19 in the inner tier are greater than the pressures at the discharge sides of these blades in the outer tier,,thereby necessitate ing the use of packing in connection with the partitions 24, 25, 26,, 27, 28, 29, 30' and 31 and the deflector .37 to minimize leakage from the inner to the outer tier.

Owing to the unavoidable leakage from the. inner tier, at 13, to the outer tier, at 14, in the construction shown in Fig ,2, where blading is of the reaction type, I preferably locate the initial partition element 24 nearer to the tip of the row of blades 20 than with the construction shown in Fig. 1, in order that a greater annulus inlet area may be provided for the inner tier 13, than tier, at 14. Steam which leaks from the in ner tier, at 13, is added to, that passing through the] outer tier, at 14, so that sub-v stantially equal amounts maybe discharged by the inner and outer portions of the last row of moving blades 23.

In Fig. 2, the blade elements 41, 35 and 36 increase in height from the inlet to the exit sides to provide for adequate area due to the expansion of steainand to the di charge thereof at an angle. WVhile I have particularly described :the low-pressure blading of Fig. 2 as being of. the reaction type, it is to be understood that this is done by wayof example only and that impulse blading could be employed just as well and my additional bladingwould cooperate just as usefully.

I11 Fig, 3, I show a further modified form of myinvention in which the blading of the inner and the outer tiers, at 13 and 14, of

the tiered section, at 12, is of the reaction type and in whichthe same pressuredissides of the rows of blades 21", 22" and 23 in the inner and int he outer tiers, at

13 and l t, respectively, are equal, it is unnecessary to use packing inconnection with the diaphragm or partition element 24 25",,26", 27, 28", 29", 30" and 81" and with the deflector or shroud element 37 to prevent leakage of steam from the inner tier, at- 13, to the outer tier, at 1ft. Even though the discharge pressures are uniform throughout the length of the last row of moving blades 23 steam will be discharged froni the inner portions 33 with a greater residual velocity energy than steam dis: charged by the outer portions ll" of the same row of blades 23. owing. to the lower blade velocity of the inner. portions 33".

As steam reaches the exhaust or terminal pressure after it is discharged from the inner blade portions 33", the vblades 555 merely serve as directing blades to properly impinge the inner. annulus of steam against the impulse blades 36 in order that the available portion of the higher residual veloc-ity energy possessed by steam of the inner annulus may be abstracted.

order to avoid excessive gauging of the blading of the outer tier, at lt, in Fig.- 3, so as to maintain high efficiency for the blading of the outer tier, the partition meme bore 24?, 25", 26/, 27", 28, 29", 30" and 31 and the deflector 37 may solocated as to provide adequate area for the outer annulus with the preservation ofsmall discharge orexit angles for. the, rows of moving blade elements of the outer tier, at 14/ The:

location of the partition elements further inward as the exhaust is approached in this way, of course, necessitates a contractionin the area of the inner annulus of the inner tier, at 13. Such contraction may be com: pensated for by proper gauging of the blade elements of the inner tier, at the high residual velocity energy of the stea m.clischarged by the inner tier or blading, at 13, being abstracted by the last row of impulse blades 36 of the additional-blading, at 15.

The blades 35 increase in height from the inlet to the discharge sides sufficiently to compensate for the narrowing of the steam passages there-between incident to discharge at small angles.

In Fig. 4,1 show a further mOCllfiQClifOI IiI of my invention in which the additional.

blading, at 15, is similarto that used in Fig. 8. In this view, the last row of moving tall blades 32 and preceding rows of blades are not tiered, as shown in Figs. 1, 2 and With this type of construction, it is essential that the pressure distribution shall be uniform throughout the blading, in other words, the discharge pressure must be the same throughout the discharge side of the last row at movinghlades32. The additional blading consists of a row of guide blades or vanes 35 carried by a deflector 37, as in Fig. 3, for properly directing steam for impingement against the row of impulse blades-36. As already pointed out, while the pressure distribution may be the same, nevertheless, with blading having a high ratio of blade height to blade diameter, the best operating efiiciency can not be main: tained throughout the height of the blade. Hence, in this modification, aswell as those already described, I design the blading so that the outer portions thereof shall move at such a speed with respect to the steam speed as to result in thebest energy abstraction, additional blading being employed at the discharge side of the inner portions of the last row-of moving blades in order that the necessarily higher residual energy of steam discharged by the inner portions may be ab,- stracted. I

It is possible, with my improved typeef turbine, to provide for uniform velocity ratios in the inner and-in the outer tiers. For example, in Fig. 2, the ratio of blade speed to steam speed may be uniform throughout the blading elements of 3 the outer tier, at 14, and the velocity ratio may be uniform throughout the blading ofthe inner tier, at 13, and the additional blading, at 15. 1

In any of the constructions aforesaid, whenever thedischarge pressure for the inner portions of-a row of blades is different from the discharge pressure of the outer portions of the same row, it is necessary to employ packing in order to minimize leakage from one tier to the other. .Such pack ingvis shown in Fig. 6. In this view, I showanembers 4A carried by partition elements in order to limit leakage. The pack: ing shown. in 6 isv of the well-known type. It is to be understood that any other suitable form (if-packing maybe used in this relation for the same purpose. v

, The operation of apparatus made in ac-. cordancefwith my invention will be apparent from the foregoing description. Steam passes through the turbine in the ordinary way, but owing to excessive differences. between the tip and root speeds of the blading at the low-pressure end, steam is discharged fromthe innerportions of the last row of moving blades with greater residual energ than that discharged from the outer p01 tions of the same row of blades. Hence, in

accordance with my invention, the low-pres.

sure blading is so designed thatthe velocity of the outerblade portions is suitable to partition elements are provided in order to define separate inner and outer tiers of blade portions and to segregate the steam passing therethrough into inner and outer annuli. This is essential if there is any difference in the pressure distribution as is the case in Figs. 1 and 2 already referred to, wherein packing is shown to minimize leakage from one tier to the other at the discharge sides of blades having different discharge pressures. I prefer to use the diaphragm or partition elements in connection with the low-pressure blading even though the discharge pressures are uniform at the exit sides of each row of blades. However, in some cases, as illustrated in Fig. 4, the partitions maybe dispensed withand the available portion'of the higher residual velocity energy of the inner portions of the last row ofmovin'g blades 36 may be abstracted by the additional blading, at 15.

From the foregoing, it will be apparent that the low-pressure blading, at 12, may be of any suitable type, that any desired distribution of pressures therein may be employed, and that the additional blading may have the stationary blade elements thereof serve merely as directing vanes or to expand steam further and that the moving blades of the additional blading may be either of the impulse-or the reaction type. It is alsoto be understood that, if desired, more than one moving row of additional blading may be employed. In other words, I desire it to be understood that the additional blading and the tall low-pressure blading may be designed in any suitable manner for the abstraction of energy from steam, and, while I prefer to use partition or diaphragm elements to divide the low-pressure blading 1nto inner and outer tiers and to segregate the steam passing therethrough into inner and:

outer annuli, it is to be understood that in some cases, as shown in Fig. 4, this feature of construction maybe omitted. Hence, I regard my invention to be the provisionof additional blading in connection with the inner portions of blading having a high ratio of blade height to blade diameter, the outer portions of the blading having a velocity suitable to the steam velocity and the add1- tional blading servingto abstract the available portion of the residual energy possessed by steam discharged by the inner portions of said high ratio blading; and, more pars ticularly, I regardas my invention the division of blading having a high, ratio ofblade height to blade diameter into inner and outer. tiers, the blading of the outer tier having a velocity suitable to the steam velocity and additional blading being employed to,

abstract the available portion of the residual ing having a uniform range of expansion fromtheroots to the tips thereof, the inner portionsfof the last moving row of such blading discharging steam with greater residual energy than the outer portions to the extent determined by the relatively lower speed of said inner portions, and additional blading for abstracting the available portion of the residual energy possessed by the steam discharged by said inner portions.

2. Ina turbine, the combination of blad inghaving a high ratio of blade height to blade diameter and a uniform range of expension from the roots to the tips thereof, partition means carried by the blading for dividing motive fluid passing therethrough into inner and outer annuli, and additional blading for abstracting the available portion of the velocity energy possessed by the inner' annulus of motive fluid discharged by said first blading.

energy in. the steam discharged by the inner 3. In a turbine, the combination of low- I pressure blading comprising a plurality of rows of stationary and moving blades, the

last row of moving blades discharging steam at the same pressure from the'roots to the tips thereof, partition means carried by such blades for dividing them into inner and outer tiers and for segregating the motive fluid passing therethrough into inner and outer annuli, and additional blading for abstracting the available portion of the residualvelocity energy possessed by the inner annulus of motive fluid discharged by the inner tier of said first blading.

4. In a turbine, the combination of lowpressure tiered'blading in which substantial energy abstraction takes place in the tiers and in which the'inner tier discharges steam with greater residual energy than the outer tier and additional blading followingthe inner tier for'abstracting the available portion of the residual-energy possessed bythe motive fluid discharged thereby.

In'testimony whereof, I have hereunto subscribed my name this 10th day of Sept. 

